The present project will compare normal and deviant infant samples in terms of their ability to abstract relational features of both the physical and social environment. It is assumed that intellective deficiency is best reflected in these functions and hence that they may provide the basis for early diagnosis of mental handicap. A variety of tasks requiring discrimination of invariant configural and temporal-causal properties will be administered to normal, Down's syndrome, and "high risk" infants at various gestational and postnatal ages during the first year of life.